UFC lightweight champion Anthony “Showtime” Pettis has been a very busy man.

In between coaching season 20 of “The Ultimate Fighter” and training for his first title defense against Gilbert Melendez, Pettis recently inked a blockbuster sponsorship with Reebok.

Since Pettis took the belt from Benson Henderson at UFC 164 last August, the champ has been repeatedly sidelined with injuries, including a nagging knee injury kept Pettis from defending his belt against Josh Thompson last December.

The title fight that has been holding up the lightweight division will finally take place on Dec. 6, nearly a year and a half after Pettis’ victory against Henderson.

“I took a lot of physical abuse getting to this title,” Pettis told The Post during an open workout at the UFC Gym in Lower Manhattan. “I’ve fought with injuries before, but that’s not smart now that I have the belt. I have to take the time to heal everything before I defend my title.”

Now “Showtime” insists time is on his side when he steps into the cage against Melendez, who also has been on the shelf for more than a year.

Anthony Pettis (left) and his brother Sergio during a workout in the shadow of the Brooklyn Bridge.Reebok

“Ring rust is not an issue for me, I’m young, I treat my injuries right, and I take the necessary time off,” Pettis told The Post. “Melendez hasn’t fought in a year as well. He fought in September, I fought in August, so we’ve been sitting on the shelf for about the same amount of time. It won’t be a disadvantage for me.”

As a backdrop for the Pettis-Melendez showdown is the endless talk of Pettis fighting featherweight champion Jose Aldo in a “battle of the champs” superfight.

Pettis exploded onto the MMA scene back in 2010 when he won the WEC lightweight belt from Henderson in their first fight. He has gone 4-1 since the UFC absorbed the WEC into its roster four years ago, meaning Pettis barely has averaged a fight per year since he debuted in the octagon against Clay Guida in 2011.

Melendez, a former Strikeforce lightweight champion, has been equally inactive since signing with the UFC in 2013, having fought just two times since Strikeforce closed up shop in 2012.

“[Melendez] is a great fighter, he’s a champ in his own right from Strikeforce,” Pettis said. “We’re coaching [against each other] on ‘The Ultimate Fighter’ right now, but man, I can’t wait to get back in the cage myself.”